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XXI. On the Self-fertiligdfion of Plants. 
By the Rev. GEoRaE HeEnstow, M.A., F.L.S., POS 
(Plate XLIV.) 
Read November 1st, 1877. 
INTRODUCTION.—No one can venture to treat of the fertilization of plants without 
being deeply indebted to the laborious investigations of Mr. Darwin, and, I would add, 
no one ought to do so without expressing his profound gratitude to that great author 
for the aid derived from his many works. Such, at least, are my own feelings, that 
while I differ in some respects from his conclusions with reference for the subject of 
this paper, I cannot proceed without first acknowledging a debt of gratitude for the 
vast stores of facts which are to be found in his writings. In order to establish what I 
believe to be the real value and effects of self-fertilization, I shall be obliged to refer 
frequently to Mr. Darwin’s latest work on the ‘Cross and Self-fertilisation of Plants,’ 
because he has therein several times stated his belief in what he calls ‘the evil effects 
and *'injuriousness" of self-fertilization—terms which, I have reason to think, not only 
fail to express accurately, but which are liable to misrepresent the real value of the pro- 
cess. It is true, there may have occurred in his experiments some individual instances 
of cultivated plants to which such terms might seem applicable; but it is not so much 
with isolated and exceptional cases that I purpose dealing as recognizing a broad and 
general principle in the vegetable kingdom, taken in its entirety—one, in fact, not 
necessarily limited to the flowering plants, but applicable to ni Aap qure as well, though 
I am not at present concerned with the latter*. 
Before addressing myself to the subject proper, I think the reader will not consider 
it out of place if I state, as briefly as possible, what are the results Mr. Darwin has 
secured to science by his latest observations—as, in order to show what I conceive to be 
the true value of self-fertilization, it will be necessary to point out the "n value of 
other kinds of crossing, so as to make the results comparative. 
There are, at least, five kinds of union, apart from hybridization proper, or the union 
of distinct species or genera :—(1) self-fertilization, or the fertilization of a pistil by the 
pollen from the same flower; (2) crossing different flowers on the same plant; (3) cross- 
ing flowers on different plants of the same stock ; (4) crossing flowers of different plants, 
* I had purposed writing this paper before I was aware that Mr. Darwin's book was coming out, and contributed 
an article on self-fertilization to * Nature,’ vol. xiv. p. 543, in which number Mr. Darwin’s book was, I think, first 
mentioned as being shortly about to appear. On subsequently restudying the question, with the aid of Mr. Darwin’s 
work, I found it necessary to thoroughly recast my paper, as he had recorded a vast number of facts quite new to 
me, and of which I have now taken advantage. I would also add that I did not study Miiller’s ‘Befruchtung der 
Blumen durch Insekten’ until I had written out all my own observations, so that wherever I have quoted or alledag 
to that acute observer’s writings, such sentences are later additions to this paper, 
SECOND SERIES.—BOTANY, VOL. I. 9v — 
